This invention relates to polysulfide modified epoxy resins.
Epoxy resins are well known in the art and have been used commercially for years. Typical epoxy resins are diglycidyl ethers of bisphenol A derived from bisphenol A and epichlorohydrin. Their widespread use in protective coatings and electrical and structural applications are a result of their exceptional combination of properties such as toughness, adhesion, chemical resistance and superior electrical properties.
Polysulfide polymers are also well known in the art and have been used commercially for many years, see, for example, U.S. Pat. Nos. 1,890,191 and 2,466,963. Such polysulfide polymers are prepared by copolymerizing metal polysulfides and polyfunctional aliphatic hydrocarbons. A very high molecular weight rubber is thereby formed, which is then cleaved with sodium hydrogen sulfide and sodium sulfite to yield a lower molecular weight mercaptan-terminated polymer. These mercaptan-terminated polymers may be cured by the use of oxidants such as metal oxides to form rubbers with desirable properties such as flexibility, adherence, resistance to light, heat, oxygen, oils, solvents and abrasion. However, the mercaptan end groups of these polymers impart a strong, disagreeable odor which limits the practical utility of these polymers.
(Vinylaryl)alkyl-terminated polysulfides prepared from a metal polysulfide and a (vinylaryl)alkyl compound are disclosed by Meyer and Dergazarian in U.S. Pat. No. 4,438,259 as lacking the strong disagreeable odors of conventional mercaptan-terminated polysulfides. Such (vinylaryl)alkyl-terminated polysulfides are curable and exhibit the desirable properties typical of the mercaptan-terminated polysulfides without the disagreeable odor. These polysulfides have utility in adhesive, sealant and caulking compositions.